1. Technical Field
A photoresist composition containing a photo radical generator (abbreviated as xe2x80x9cPRGxe2x80x9d) is disclosed. In particular, a photoresist composition is disclosed which comprises (a) a photoresist resin, (b) a photoacid generator, (c) an organic solvent and (d) a photo radical generator. The photo radical generator reduces or prevents sloping pattern and I/D Bias due to a higher concentration of acid in the upper portion of the photoresist relative to the concentration of acid in the lower portion of the photoresist.
2. Description of the Related Art
Use of chemical amplification-type photoresists (i.e., photoresist compositions) is currently being investigated in photolithography processes using light source such as KrF, ArF, VUV and EUV to achieve a high sensitivity in a minute image-formation on semiconductor devices. Such photoresist compositions are generally prepared by blending a photoacid generator with a matrix resin polymer (i.e., photoresist polymer or photoresist resin) having an acid labile group.
In a photolithography process, the resolution of an image depends on the wavelength of the light used. Thus, the shorter the wavelength, the higher the resolution, i.e., shorter wavelengths allow smaller pattern formation.
In order to be useful in a photolithography process, a photoresist composition must have an excellent etching resistance, heat resistance, and adhesiveness. Moreover, to reduce the cost of manufacturing semiconductor devices, a photoresist composition should be capable of being developed with a common developing solution, such as commonly available 2.38 wt % aqueous tetramethylammonium hydroxide (TMAH) solution. These qualities are particularly important in photolithography processes utilizing a deep ultraviolet light source (i.e., short wavelength light source), including KrF (248 nm), ArF (193 nm), VUV (157 nm) and EUV (13 nm).
However, it is very difficult to synthesize a photoresist composition that satisfies all of these requirements. For example, a photoresist polymer having a polyacrylate backbone is readily available, but it has poor etching resistance and is difficult to develop.
Etching resistance may be improved by adding alicyclic unit to the photoresist polymer. However, the presence of alicyclic unit in the photoresist polymer creates problems during the process for manufacturing semiconductor elements. For example, a detrimental sloping pattern is formed when photoresist resin comprising the alicyclic units is used.
When the resin has low light absorbance, a vertical pattern is generated as shown in FIG. 1a. When a chemically amplified photoresist composition comprising the alicyclic units is used, the sloping pattern is formed since more light exposure is performed on the upper portions of the photoresist (PR) composition relative to the lower portion of the PR composition (See FIG. 1b). It is believed that the higher light exposure on the upper portions is due to an aerial image of the PR composition (or absorption of light by the resin).
Therefore, there is a need for a photoresist composition which overcomes the above-mentioned disadvantages.
Photoresist compositions are disclosed which significantly reduce or prevent formation of a sloping pattern due to a higher concentration of generated acid in the upper portions of the photoresist compositions relative to the lower portions of the photoresist compositions.
A semiconductor element produced by using the disclosed photoresist composition is also disclosed.